• Journal of Korean Society on Water Environment
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• v.37 no.6
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• pp.449-457
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• 2021

Photosynthesis and respiration rate of microalgae are important factors during advanced wastewater treatment research using microalgae, There are several equipments and measurement methods for measuring photosynthesis and respiration, with different challenges that occur during pretreatment and stabilization of the analysis process. Therefore, in this study, for accurate Photosynthesis and Respiration (P&R) analyzer measurement, the analysis process was divided into pre-processing, DO stabilization, and analysis stages and each was optimized to enable accurate evaluation. For this purpose, the effect of DO saturation of the sample on P&R analysis, DO stabilization according to the degassing flow rate, and photoinhibition of the OD level on photosynthesis was investigated. Based on our study results, when DO was supersaturated, photosynthetic efficiency decreased due to photorespiration, making it inappropriate as a P&R sample. In addition, 0.5 L-N2/min level was the optimal nitrogen degassing flow rate for DO desaturation. The inhibition of photosynthetic efficiency by self-shading caused by the increase in OD was observed from OD 2.0, and it was found that P& R analysis is preferably performed on samples with OD less than 2.0. In addition, based on the above three optimization results, an optimized P&R Analyzer instruction for accurate P&R analysis was also presented.

• Membrane and Water Treatment
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• v.15 no.2
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• pp.51-57
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• 2024

The removal of phosphorus, especially phosphate-form phosphorus, is necessary in wastewater treatment. Biofouling induced by the quorum sensing mechanism is also a major problem in membrane bioreactor (MBR), which reduces membrane flux. This study introduces lanthanum-doped quorum quenching (QQ) beads into MBR, confirming their inhibitory effect on biofouling due to Rhodococcus sp. BH4 and their capacity for phosphorus removal through lanthanum adsorption. A batch test was conducted to access the phosphate adsorption of lanthanum-QQ (La-QQ) beads and lab-scale MBR to verify the effect of inhibition. The study aimed to identify distinctions among the MBR, QQ MBR, and La-QQ MBR. In the batch test, the phosphate removal rate increased as the volume of beads increased, while the unit volume removal rate of phosphate decreased. In the lab-scale MBR, the phosphate removal rates were below 20% in the control MBR and QQ MBR, whereas the La-QQ MBR achieved a phosphate removal rate of 74%. There was not much difference between the ammonia and total organic carbon (TOC) removal rates. Regarding the change in transmembrane pressure(TMP), 3.7 days were taken for the control MBR to reach critical pressure. In contrast, the QQ-MBR took 9.8 days, and the La-QQ MBR took 6.1 days, which confirms the delay in biofouling. It is expected that La-QQ can be used within MBR to design a more stable MBR process that regulates biofouling and enhances phosphate removal.

• Journal of Marine Life Science
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• v.1 no.1
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• pp.1-7
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• 2016

In order to assess seasonal and geographical characteristics of pollutant Escherichia coli, we investigated its distribution in Nakdong River mouth and Busan coastal water from February 2013 to November 2015. The coastal area was divided into five different zones (I-V) based on the pollutant level and geographical characteristics. During the study periods, water temperature and salinity varied from 7.50 to 27.64℃ and 16.82 to 34.82 psu, respectively. The annual water temperature variation was characterized in temperate zone. The salinity was significantly (p<0.05) decreased in zone IV and zone III after heavy rain during summer season in 2014, resulting led to elevated E. coli biomass. The highest colony formation of E. coli was recorded at 6,000 cfu l^-1 during autumn at station 1 (zone I). On the other hands, during all seasons of 2015, E. coli abundances were kept to be low level in zone III. The E. coli was not significantly (p>0.05) correlated with water temperature. However, the salinity was significantly (r=-0.53, p<0.05) correlated with the E. coli, implying that salinity plays a crucial role in the proliferation of E. coli. Consequently, E. coli in western Busan coastal water might have been significantly promoted by pollutant sources from Nakdong Rive discharge during the spring and summer rainy seasons depending on annual rainfall variations. On the other hands, E. coli in station 1 (i.e., Suyeong Bay) was obviously high due to influences of discharge water from municipal wastewater treatment plant. However, there was no clear seasonality of E. coli.

• Journal of Korean Society on Water Environment
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• v.22 no.4
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• pp.590-598
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• 2006

In-situ Air sparging (IAS) is a groundwater remediation technique, in which organic contaminants volatilize into air form the saturated to vadose zone. This study was carried out to evaluate the effect of sludge and soil microbial community structure on air sparging of Total Petroleum Hydrocarbons (TPH) contaminated groundwater soils. In the laboratory, diesel (10,000 mg TPH/kg) contaminated saturated soil. The Air was injected in intermittent (Q=1500 mL/min, 10 minute injection and 10 minute idle) modes. For Terminal-Restriction Fragment Length Polymorphism (T-RFLP) analysis of eubacterial communities in sludge of wastewater treatment plants and soil of experiment site, the 16S rDNA was amplified by Polymerase Chain Reaction (PCR) from the sludge and the soil. The obtained 16S rDNA fragments were digested with Msp I and separated by electrophoresis gel. We found various sequence types for experiment with sludge soil samples that were closely related to Agrococcus, Flavobacterium, Thermoanaerobacter, Flexibacter and Shewanella, etc, in the clone library. The results of the present study suggests that T-RFLP method may be applied as a useful tool for the monitoring in the TPH contaminated soil the fate of microorganisms in natural microbial community.

• Journal of Korean Society on Water Environment
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• v.26 no.5
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• pp.754-760
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• 2010

This study was carried out not only to evaluate optimal operating condition to increase biogas production, but also to estimate feasibility of renewable energy from anaerobic digester of sewage sludge. Semi- continuous Fed and Mixed Reactors (SCFMRs) were operated in various condition to quantify the reactor variables. The result of SCFMR operation showed that the biogas productivity and total volatile solids (TVS) removal of total solids (TS) 4% reactor at hydraulic retention time (HRT) 20 days with Organic Loading Rate (OLR) of $1.45kg/m^3-d$ were $0.39m^3/m^3-d$ and 26.7%, respectively which was two times higher than that of TS 2.5% reactor. Consequently the daily biogas production of $20,000m^3$ would be possible from the total volume of $52,000m^3$ of anaerobic digesters of the municipal wastewater treatment plant in D city. In feasibility study for the Biogas utilization, combined heat and power system (CHP) and CNG gasification were examined. In case of CHP, the withdrawal period of capital cost for gas-engine (GE) and micro gas-turbine (MGT) were 7.7 years and 9.1 years respectively. biogas utilization as Clean Natural Gas (CNG) shows lower capital cost and higher profit than that of CHP system. CNG gasificaion after biogas purification is likely the best alternative for Biogas utilization which have more economic potential than CHP system. The withdrawal period of capital cost appeared to be 2.3 years.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.795-798
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• 2003

Toxic organics are of great environmental concern primarily because they are toxic to mammals and birds, and are relatively soluble in water to contaminate surface water and groundwater. In this study, the decomposition of phenol, a widely used organic, in aqueous solutions by Boron doped diamond(BDD) electrode was examined. Thin, Boron-doped conducting diamond films are expected to be excellent electrodes for industrial electrolysis. Boron-doped diamond (BDD) were used as anode for generating ozone gas by electrolysis of acid solution. In this work. we have studied ozone generating system using BDD electrode. In order to determine the ozone generation properties of diamond electrode, experimental conditions, electrolyte concentration, temperature, flow rate and reaction time were varied diversely. As a result, we could confirm that ozone gas was generated successfully and the performance of diamond electrode was stable for electrolyte while $PbO_2$ electrode was disintegrated. Actually we are found that ozone amount increased by lowering the temperature of electrolyte. Decomposition of phenol concentration in the reaction solution by photolytic ozonation( $UV/O_3$) was analyzed by HPLC epuipped with a UV detector.

• Membrane Journal
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• v.11 no.4
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• pp.179-189
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• 2001

Effect of ozonation on permeate flux was studied by using polysulfone ultrafiltration membrane. The filtration was first carried out by permeating phenol solutions under 3$kg_{f}$/$cm^2$ until steady-state flux was obtained. Then, the ozone of concentration range between 10 and 45 mg/1.min was ozonated in water for reducing the fouling on the UF membrane. Treatment of chemical wastewater by combined ozone and membrane filtration methods was also investigated for the final purpose. The Fenton method assisted by chemical coagulation was employed as a prtreatment method and found to be highly efficient in removing a large amount of organic compounds. And it was found that the ozonation made the permeate flux enhance in the phenol solution and phenolic-chemical wastewaster by 10% and oxidation by ozone and hydrogen peroxide was more effective. Evidence was presented that TMP decreased in more ozone concentrated water and it was found that the ozone-mediated membrane would have a limited role to prevent the membrane fouling rather than to eliminate fully.

• Journal of the Korean earth science society
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• v.45 no.1
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• pp.72-84
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• 2024

Recently, the vulnerability of water resources has been increasing owing to climate change, highlighting the importance of groundwater. In particular, the Nakdong River Basin, located in the southern part of Korea, experiences frequent water scarcity phenomena, such as droughts. This study analyzed the hydrogeological characteristics of the study area by examining groundwater and stream water in the Gwangrye Stream, downstream of the Nakdong River Basin, in August and October 2023. Therefore, we collected samples from 54 groundwater wells and five streams for water quality analysis. The results of the field tests indicated an increasing trend in electrical conductivity from upstream to downstream in the study area. Laboratory analyses confirmed that the concentration of Na increased from upstream to downstream more than that of Ca. In conclusion, both stream water and groundwater were influenced by anthropogenic contamination. These changes were closely related to land use in the study area. The upstream areas are primarily composed of forests, whereas the downstream areas are composed of industrial complexes, wastewater treatment facilities, and agricultural areas, which are likely to affect both stream water and groundwater.

• Journal of Korean Society on Water Environment
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• v.16 no.4
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• pp.501-512
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• 2000

This study was carried out to develop the new process for RBC process which is capable of nutrient removal and to obtain its design parameters for Sludge Settling Type Rotating Biological Contactors by comparing RBC with RBC combined with HBR (Hanmee Bio-Reactor). To achieve more than 90% of organic removal efficiency, organic loading rate less than $6.0g\;BOD/m^2/d$ is recommended. Nitrification rate was about 90% at $6.0g\;BOD/m^2/d$. TN removal efficiency of RBC+HBR was higher than those of RBC1 and RBC2. TN removal efficiency at condition of $5.0g\;BOD/m^2/d$ was about 60% in RBC1. When BOD loading rate was $6.0g\;BOD/m^2/d$. TN removal efficiencies in RBC2 and RBC+HBR were about 70%, 80%, respectively. TP removal efficiency was more than about 67% for RBC1, about 63% for RBC2 and about 71 % for RBC+HBR at the same loading rate. From the blank experiment to observe removal efficiency in the first stage, it can be known that COD removal efficiency was about 30% and suspend solids settling rate was about 45%. It was proved that RBC+HBR is much better in sludge dewatering than RBC.

• Journal of Korean Society on Water Environment
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• v.21 no.1
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• pp.73-78
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• 2005

This study was performed to examine the disinfection capability of a Rotating Activated Bacillus Contactor (RABC) system, in which the predominant species, Bacillus sp. was expected to have a removal or inactivation effect of total coliforms. In a settling test with mixtures of E. coli and Bacillus sp., a high removal of E. coli was observed at $20{\sim}40^{\circ}C$, while insignificant removal at $10^{\circ}C$. In a batch test, a 4.5% addition of Bacillus sp. to activated sludge considerably enhanced the removal effect of total coliforms, indicating Bacillus sp. played an important role in improving the settlability of the sludge and coliforms. In a pilot scale RABC system, the concentration of total colifroms reduced remarkably in the settling tank, suggesting that total coliforms in the RABC process were eliminated through coagulation and precipitation, probably due to extracellular polymeric substance (EPS) of Bacillus sp. The fraction of Bacillus sp. in the total cell count in the RABC process was in the range of 4.5%~6.3%. The majority (75%) of the Bacillus sp. in the RABC process was Bacillus subtilis which is known to enhance coagulation and precipitation by producing EPS. Hence, an adoption of a RABC process might be able to eliminate the disinfection unit process from a wastewater treatment system.